Paul Grosu
2015-Nov-17 01:11 UTC
[Rd] Small request of a feature improvement in the next version of R
Hi Everyone, Sorry to bother the list with this small request, but I've run into this issue and was wondering if it could be fixed in the next version of R. Sorry if it was raised in a previous thread: So when I try the following I get an error:> m <- list() > m[["A3V6HVSALQ835D"]][['profiles']] <- 3 > m[["A3V6HVSALQ835D"]][['stars']] <- c(1, 23)Error in m[["A3V6HVSALQ835D"]][["stars"]] <- c(1, 23) : more elements supplied than there are to replace As does the following:> m <- list() > m[["A3V6HVSALQ835D"]][['profiles']] <- c() > m[["A3V6HVSALQ835D"]][['stars']] <- c() > m[["A3V6HVSALQ835D"]][['profiles']] <- 3 > m[["A3V6HVSALQ835D"]][['stars']] <- c(1, 23)Error in m[["A3V6HVSALQ835D"]][["stars"]] <- c(1, 23) : more elements supplied than there are to replace But when I reverse the order, I don't:> m <- list() > m[["A3V6HVSALQ835D"]][['stars']] <- c(1, 23) > m[["A3V6HVSALQ835D"]][['profiles']] <- 3As doesn't the following, with the order reversed for the assignment:> m <- list() > m[["A3V6HVSALQ835D"]][['profiles']] <- c() > m[["A3V6HVSALQ835D"]][['stars']] <- c() > m[["A3V6HVSALQ835D"]][['stars']] <- c(1, 23) > m[["A3V6HVSALQ835D"]][['profiles']] <- 3And when I instantiate it in this way, it does not with the original order:> m <- list() > m[["A3V6HVSALQ835D"]][['profiles']] <- c() > m[["A3V6HVSALQ835D"]][['stars']] <- list() > m[["A3V6HVSALQ835D"]][['profiles']] <- 3 > m[["A3V6HVSALQ835D"]][['stars']] <- c(1, 23)The request is so that order-specific assignments would not throw an error, and I am using version 3.2.2 of R. Thank you, Paul
Martyn Plummer
2015-Nov-17 10:13 UTC
[Rd] Small request of a feature improvement in the next version of R
On Mon, 2015-11-16 at 20:11 -0500, Paul Grosu wrote:> Hi Everyone, > > Sorry to bother the list with this small request, but I've run into this > issue and was wondering if it could be fixed in the next version of R. > Sorry if it was raised in a previous thread: > > So when I try the following I get an error: > > > m <- list() > > m[["A3V6HVSALQ835D"]][['profiles']] <- 3 > > m[["A3V6HVSALQ835D"]][['stars']] <- c(1, 23) > Error in m[["A3V6HVSALQ835D"]][["stars"]] <- c(1, 23) : > more elements supplied than there are to replace > > As does the following: > > > m <- list() > > m[["A3V6HVSALQ835D"]][['profiles']] <- c() > > m[["A3V6HVSALQ835D"]][['stars']] <- c() > > m[["A3V6HVSALQ835D"]][['profiles']] <- 3 > > m[["A3V6HVSALQ835D"]][['stars']] <- c(1, 23) > Error in m[["A3V6HVSALQ835D"]][["stars"]] <- c(1, 23) : > more elements supplied than there are to replace > > But when I reverse the order, I don't: > > > m <- list() > > m[["A3V6HVSALQ835D"]][['stars']] <- c(1, 23) > > m[["A3V6HVSALQ835D"]][['profiles']] <- 3 > > As doesn't the following, with the order reversed for the assignment: > > > m <- list() > > m[["A3V6HVSALQ835D"]][['profiles']] <- c() > > m[["A3V6HVSALQ835D"]][['stars']] <- c() > > m[["A3V6HVSALQ835D"]][['stars']] <- c(1, 23) > > m[["A3V6HVSALQ835D"]][['profiles']] <- 3 > > And when I instantiate it in this way, it does not with the original order: > > > m <- list() > > m[["A3V6HVSALQ835D"]][['profiles']] <- c() > > m[["A3V6HVSALQ835D"]][['stars']] <- list() > > m[["A3V6HVSALQ835D"]][['profiles']] <- 3 > > m[["A3V6HVSALQ835D"]][['stars']] <- c(1, 23) > > The request is so that order-specific assignments would not throw an error, > and I am using version 3.2.2 of R.Your example combines two nested calls to the replacement function "[[<-". It is a lot easier to understand what is going wrong if you break this down into two separate function calls. First, the element of m that you want to modify is NULL:> m <- list() > m[["A3V"]]NULL So the expression> m[["A3V"]][['profile']] <- 3is equivalent to:> tmp <- NULL > tmp[['profile']] <- 3 > m[["A3V"]] <- tmpInspecting the result:> m$A3V profile 3> class(m$A3V)[1] "numeric" So m$A3V is a numeric vector and not, as you expected, a list. This behaviour of "[[<-" when applied to NULL objects is documented on the help page: See help("[[<-") The solution is to create m[["A3V"]] as a list before modifying its elements:> m <- list() > m[["A3V"]] <- list()... Martyn> Thank you, > Paul > > ______________________________________________ > R-devel at r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel----------------------------------------------------------------------- This message and its attachments are strictly confidenti...{{dropped:8}}
Paul Grosu
2015-Nov-22 04:11 UTC
[Rd] Small request of a feature improvement in the next version of R
Hi Martyn, I understand now what is happening and thank you for the nice explanation. I am wondering now, based on the following definition: "When $<- is applied to a NULL x, it first coerces x to list(). This is what also happens with [[<- if the replacement value value is of length greater than one: if value has length 1 or 0, x is first coerced to a zero-length vector of the type of value." The following works as expected: m <- list() m$"A3V6HVSALQ835D"$'profiles' <- 3 m$"A3V6HVSALQ835D"$'stars' <- c(1, 23) But if the object encapsulating them (m) is already a list, why would it not be sensible for any [[<- assignments underneath it be automatically converted to a list? It would be nice to have it automatically have m become a list if one performs m[["A3V6HVSALQ835D"]][['profiles']] <- 3 on the first assignment - without having to instantiate m to a list (i.e. m <- list()). Since R is heavily influenced by SEXP this would be as natural as a cons(). For instance, I can create a list of functions but not with any other type:> a <- function(something="Hi") { print( something ) } > b <- a > list( a, b )[[1]]()[1] "Hi"> list( a, b )[[2]]("there :)")[1] "there :)" In fact vectors become lists:> c(a,b)[[1]] function (something = "Hi") { print(something) } [[2]] function (something = "Hi") { print(something) } Even matrices become lists:> as.matrix(c(a,b))[,1] [1,] ? [2,] ?> as.matrix(c(a,b))[1][[1]] function (something = "Hi") { print(something) }> as.matrix(c(a,b))[2][[1]] function (something = "Hi") { print(something) } Since all become lists and the assignments are list-like, then it would be nice to have the children of a list to automatically become a list, even when they are accessed like a list and the parent (m) is not instantiated as a list, which should automatically become a list. I know I wrote a lot, but let me know if I should expand on anything for clarification purposes. Thank you, Paul -----Original Message----- From: Martyn Plummer [mailto:plummerm at iarc.fr] Sent: Tuesday, November 17, 2015 5:13 AM To: pgrosu at gmail.com Cc: r-devel at r-project.org Subject: Re: [Rd] Small request of a feature improvement in the next version of R On Mon, 2015-11-16 at 20:11 -0500, Paul Grosu wrote:> Hi Everyone, > > Sorry to bother the list with this small request, but I've run into > this issue and was wondering if it could be fixed in the next version ofR.> Sorry if it was raised in a previous thread: > > So when I try the following I get an error: > > > m <- list() > > m[["A3V6HVSALQ835D"]][['profiles']] <- 3 > > m[["A3V6HVSALQ835D"]][['stars']] <- c(1, 23) > Error in m[["A3V6HVSALQ835D"]][["stars"]] <- c(1, 23) : > more elements supplied than there are to replace > > As does the following: > > > m <- list() > > m[["A3V6HVSALQ835D"]][['profiles']] <- c() > > m[["A3V6HVSALQ835D"]][['stars']] <- c() > > m[["A3V6HVSALQ835D"]][['profiles']] <- 3 > > m[["A3V6HVSALQ835D"]][['stars']] <- c(1, 23) > Error in m[["A3V6HVSALQ835D"]][["stars"]] <- c(1, 23) : > more elements supplied than there are to replace > > But when I reverse the order, I don't: > > > m <- list() > > m[["A3V6HVSALQ835D"]][['stars']] <- c(1, 23) > > m[["A3V6HVSALQ835D"]][['profiles']] <- 3 > > As doesn't the following, with the order reversed for the assignment: > > > m <- list() > > m[["A3V6HVSALQ835D"]][['profiles']] <- c() > > m[["A3V6HVSALQ835D"]][['stars']] <- c() > > m[["A3V6HVSALQ835D"]][['stars']] <- c(1, 23) > > m[["A3V6HVSALQ835D"]][['profiles']] <- 3 > > And when I instantiate it in this way, it does not with the originalorder:> > > m <- list() > > m[["A3V6HVSALQ835D"]][['profiles']] <- c() > > m[["A3V6HVSALQ835D"]][['stars']] <- list() > > m[["A3V6HVSALQ835D"]][['profiles']] <- 3 > > m[["A3V6HVSALQ835D"]][['stars']] <- c(1, 23) > > The request is so that order-specific assignments would not throw an > error, and I am using version 3.2.2 of R.Your example combines two nested calls to the replacement function "[[<-". It is a lot easier to understand what is going wrong if you break this down into two separate function calls. First, the element of m that you want to modify is NULL:> m <- list() > m[["A3V"]]NULL So the expression> m[["A3V"]][['profile']] <- 3is equivalent to:> tmp <- NULL > tmp[['profile']] <- 3 > m[["A3V"]] <- tmpInspecting the result:> m$A3V profile 3> class(m$A3V)[1] "numeric" So m$A3V is a numeric vector and not, as you expected, a list. This behaviour of "[[<-" when applied to NULL objects is documented on the help page: See help("[[<-") The solution is to create m[["A3V"]] as a list before modifying its elements:> m <- list() > m[["A3V"]] <- list()... Martyn> Thank you, > Paul > > ______________________________________________ > R-devel at r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel----------------------------------------------------------------------- This message and its attachments are strictly confidenti...{{dropped:8}}